In recent years, there has been a great deal of attention paid to the need to upgrade the telephone network and increase the available bandwidth. Traffic on the World Wide Web is growing at over 70% per year, and other such networks are growing even faster. There have been a number of photonic solutions offered that increase the available bandwidth of the telephone network. These solutions range from point to point connections to wavelength division multiplexed passive optical networks systems. The latter solution is very effective in principle, however the cost associated with photonic devices in these systems is an impediment to their acceptance and rapid deployment. Much of this cost is associated with the cost of packaging individual transmitters and receivers.
Recently, proposals for wavelength multiplexed passive systems have been put forth which utilize an optical modulator at the subscriber location to replace the active LED or laser devices that are typically used in prior art systems. See, for example, L. Altwegg, A Azizi, P. Vogel, Y. Wang, and P. Wiler, "LOCNET--a fiber-in-the-loop system with no light-source at the subscriber end", J. of Lightwave Tech., vol. 12, no. 3, pp. 535-540, 1994; also see: N. J. Prigo, P. D. Magill, T. E. Darcie, P. P. Iannone, M. M. Downs, B. N. Desai, U. Koren, T. L. Koch, C Dragone, and H. M. Presby, "RITE-Net: A passive optical network architecture based on the remote interrogation of terminal equipment," Proc. of the Optical Fiber Conference--post deadline session, (San Jose, Calif., Feb. 20-25, 1994) pp. 43-47. This approach has several advantages, among them lower cost and higher reliability. The passive devices are also less sensitive to temperature variations, and have a robustness suitable for the uncontrolled environment of some customer locations. Additionally, wavelength routing in the network is more reliable since the upstream light is identically the same wavelength as the downstream light.
We have developed a low-cost silicon optical modulator based on micro electro mechanical systems principles (MEMS) which fulfills the foregoing objectives, e.g. a low-cost, high production volume, modulator. The device has been designated MARS, for Moving Anti-Reflection Switch.
Typically, more than 90% of the cost of a packaged photonic device can be attributed to the package itself. In addition to the problems associated with packaging electrical chips, optoelectronic chips have an additional complication of aligning a small active optical region of the active device to the small core of an optical fiber (typically of the order of 8 .mu.m in diameter), and keeping it aligned over long term. For most photonic devices intended for telecommunications the fiber-to-device alignment tolerance is of the order of one micron. Since the MARS device is a surface normal device (light signal is normal to the plane of the optoelectronic chip) with a relatively large active area (&gt;20 .mu.m), various non-traditional packaging approaches can be employed that use passive techniques even for aligning to single mode optical fiber. Use of passive alignment reduces the number of high cost hand operations in manufacture, thereby reducing the major cost element.